One issue present in an internal combustion engine is related to a low temperature of an engine block at the start of operation of the engine. The low temperature of the engine block at the start of operation of the engine undesirably leads to higher mechanical friction. The higher mechanical friction causes higher fuel consumption and higher carbon dioxide (CO2) emissions. The issue especially occurs in a gasoline/electric hybrid vehicle, including “Stop/Start” conditions, where the internal combustion engine typically remains at a lower temperature in comparison to the internal combustion engine in a non-hybrid vehicle. The internal combustion engine of the hybrid vehicle remains at a lower temperature due to the occurrence of frequent shut-down periods such as when the hybrid vehicle is operating in an electric mode.
It is therefore desirable for the internal combustion engine to utilize recirculated fluids as heat sources to aid in regulating the temperature of the internal combustion engine. Typical examples of systems utilizing recirculated fluids are a Exhaust Gas Recirculation (EGR) system and a separate Exhaust Heat Recovery System (EHRS). Such systems may for example utilize an exchange of heat energy between the exhaust gases of the internal combustion engine and the coolant of the coolant system used to regulate the temperature of the engine block of the internal combustion engine.
The EHRS recovers the heat energy of exhaust gases following a starting of the engine, thereby minimizing the fuel consumption and the CO2 emissions of the engine. One condition that may arise during the transfer of the heat energy between the coolant and the exhaust gases relates to an undesired supercooling of the coolant immediately following the starting of the engine. The thermal inertia of the EHRS in periods of time following the starting of the engine may result in low temperature exhaust gases exchanging heat energy with the coolant, thereby resulting in a situation where the coolant being relied upon to initially aid in heating the engine block is actually disadvantageously cooled within the EHRS. The cooling of the coolant causes the heating of the engine block to be negatively affected.
Another condition associated with the internal combustion engine utilizing the EGR system occurs during a stabilized run of the engine. During the stabilized run of the engine, the EGR system may in some instances transfer heat energy from the exhaust gases to the coolant wherein the heat transfer demand on the main coolant radiator is increased due to an excessive heating of the coolant beyond a desired temperature. The increased heat transfer results in the need for a larger heat exchanger with a higher aerodynamic drag, which in turn leads to higher fuel consumption and a loss of component packaging space within the vehicle. The energy dissipated by such a process is not of any use for recirculation and therefore, further lowers an efficiency of the system.
It would be desirable to provide an improved thermal energy management system that effectively regulates the temperate of the internal combustion engine by utilizing heat energy of exhaust gases exiting the internal combustion engine.
To provide the improved thermal energy system, it is desirable to add a Latent Heat Storage Unit (LHSU) to aid the thermal energy system in heating the coolant during the initial phases of warming of the internal combustion engine. The system including the LHSU further includes a two fluid EHRS utilizing a transfer of heat energy between the exhaust gases and the coolant of the engine. It may be further desirable to combine the EGR system and the EHRS into an integrated system having a single heat exchanger common to each system that is in heat exchange relationship with all three of the coolant, the exhaust gases, and the LHSU. Different combinations of exhaust gas routing may be achieved by use of two proportional valves and one On/Off or proportional valve on the EGR system. It is further desirable for the LHSU to reduce the amount of heat energy to be dissipated to the atmosphere by accumulating the heat energy, wherein the accumulated heat energy is reused after the engine start in order to minimize fuel consumption of the internal combustion engine while also minimizing the demand on the radiator to conduct heat energy transfer. The minimizing the demand on the radiator allows for minimizing a size of the radiator, which in turn minimizing an aerodynamic drag of the radiator to aid in minimizing the fuel consumption and CO2 emissions of the vehicle.
There also exists a need for a separate oil cooler or water cooled oil cooler to aid in cooling oil used to lubricate the internal combustion engine while the engine is running in a stabilized phase. Accordingly, it is further desirable to utilize a three fluid EHRS that enables for a transfer of heat energy between the coolant, the exhaust gases, and the engine oil to efficiently manage a temperature of the engine block.